1. Field of the Invention
The present intention relates to the preparation of synthetic detergent (syndet) bar soap composition useful for washing and cleaning hands and other body parts for preventing the risk of infections caused by microorganisms which can also be efficaciously employed on other sanitizable animate and inanimate surfaces. More particularly, this invention pertains to the preparation of acidic syndet bar soap compositions and the material which results therefrom.
2. Description of Related Art
Typically soaps are prepared under conditions at above neutral pH. Thus the pH may be neutral or alkaline during preparation. At such pH levels, microorganisms can remain viable on the contaminated soaps. These can be transferred to the surface being treated by the soap. Additionally, spoilage microorganisms can multiply on the soap. Antimicrobial agents are often incorporated into such soaps to prevent microbial growth. However, such antimicrobial agents do not exhibit full antimicrobial potential due to the neutral or alkaline pH of the surrounding environment.
Synthetic detergent (syndet) bar soaps, are based on detergency of surface-active agents (synthetic detergents) instead of alkali salt or fatty acids used in conventional soaps. Because syndet soaps clean and lather like conventional soaps, general public often refers to syndet type compositions simply as soaps. Surface active agents incorporated in hand and toilet soaps remove soil and dirt from the surface of the skin or hair along with some microorganisms. However, these soaps may not kill microorganisms. Bar soaps may be contaminated with bacteria and even transmit these microorganisms during their use. Thus the use of soaps without antibacterial properties may even add microorganisms to the skin surfaces and be a vector for transmission of infections. Thus, these soaps cannot be relied upon to prevent spread of infective germs.
Antibacterial and bactericidal soaps used for personal and health care applications typically are soaps which incorporate various antimicrobial agents in addition to the surface-active agents at pH greater than 7.0 (neutrality). Antibacterial agents are often incorporated in soaps to prevent growth of microorganisms in the soap rather than as effective agents for reducing or eliminating germs on the surfaces being cleaned.
Thus, soaps labeled as xe2x80x9cantibacterialxe2x80x9d may prevent or inhibit the growth of microorganisms on the soap surface or in the soap matrix but not offer protection by killing germs on the contact surfaces, such as skin, hair or the like. Such antibacterial soaps cannot be routinely classified as xe2x80x9csanitizingxe2x80x9d soaps. Only a few types of antibacterial soaps can reduce microbial populations on the skin, hair or other body parts. These contain antibacterial agents specifically selected for such activity. These commonly used antibacterial ingredients include esters of para-hydroxybenzoic acid xe2x80x9cparabensxe2x80x9d (such as methyl parabens, propyl parabens, butyl parabens, and ethyl parabens), ethyl alcohol, imidazolidinyl urea, isothiazolin compounds, triclosan, dehydroacetate, o-phenyl phenol, quaternium compounds, boric acid, formaldehyde solutions, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT).
These materials typically are prepared and employed in compositions at neutral to alkaline pH. Fatty acid soaps must be prepared at neutral or alkaline conditions in order preserve the cleaning properties of the given soap. Synthetic detergent soaps are prepared in a similar manner as it has been held that neutral or alkaline pH levels are required to achieve proper cleaning characteristics of the soap material.
Conventional soap compositions for skin care which achieve suitable levels of sanitization are high in cost or are toxic. Chlorine based products are harmful to the environment; also certain chlorine based products are not available to the public except in health-care institutions. Thus, a sanitizing soap which would be environmentally friendly and less toxic would be highly desirable. It would also be desirable to provide a sanitizing soap which is economical and microbicidal for preventing surface or topical infection without the drawbacks of available sanitizing soap products.
Anionic surfactants have been proposed for use in cleaning compositions as well as in sanitizers or disinfecting solutions. However, for use as soap, the anionic surfactant must be present in sufficient amount to generate foam for cleaning purposes, such as washing hands and for general personal hygiene, facial conditioning, and the like. The use of high concentration anionic surfactants and other surfactant containing compositions at low pH has been held to result in damage to the skin, dryness, cracking, chapping, and irritation of the skin. Thus, anionic surfactants at low pH have not been used as microbicidal and sanitizing soaps on skin and body surfaces.
Additionally, some of the antimicrobial agents used in bar soaps, such as triclosan, have been reported to enhance antibiotic resistance in certain strains of bacteria. It is feared that their use could create the risk of propagating drug resistant bacteria and transmitting such bacteria to multiple users of the bar soap. Preparation of bar soap which would have antimicrobial properties but permit elimination or reduction in the use of such antimicrobial agents would be highly desirable.
The need to provide good lathering cleaning and sanitizing soaps is still largely unfilled. Thus, it would be desirable to provide a method for preparing a syndet soap having good cleaning characteristics which also has enhanced effective sanitizing attributes. It would also be desirable to provide syndet soaps which are acidic in nature and can exhibit antimicrobial properties. It would also be beneficial to provide a syndet bar soap which would permit the incorporation of materials, such as alpha-hydroxy acids, to facilitate and promote beneficial healing and rejuvenating of the skin.
The present invention is a synthetic detergent bar soap and method for making the same which is prepared under acidic conditions to enhance or provide antimicrobial properties to the material thus prepared. The material thus prepared exhibits at least one of the following advantages: a) under acidic conditions, the soap composition exhibits antimicrobial properties inhibiting survival and growth of microorganisms on the soap surface and on contact surfaces; b) the activity of antibacterial agents used in the soap can also be enhanced under acidic conditions; c) addition of alpha hydroxy-acids can also have beneficial effect in rejuvenating skin.
Thus the preparation of syndet soaps under acidic conditions can have cost savings or economic advantage in eliminating or reducing the amount or concentration of antimicrobial agents employed in the composition. Antimicrobial agents that are normally incorporated in antimicrobial soaps exhibit enhanced antimicrobial action under acidic conditions. Thus, the antimicrobial properties of materials already incorporated in the syndet bar soap can be further enhanced by addition of antimicrobial agents. Because of the enhanced antimicrobial activity under acidic conditions, the amount or concentration of antimicrobial agents can be reduced. This will provide an additional cost savings.
The soap composition consists essentially of:
a) an anionic surfactant present in an amount in the range from about 0.10 weight % to about 95.0 weight % based on the total weight of the concentrate composition; and
b) an acidifying agent present in an amount sufficient to provide a pH below 5.0.
The present invention is predicated on the unexpected discovery that an effective synthetic detergent bar soap can be prepared under acidic conditions which will exhibit antimicrobial characteristics. The syndet bar soap composition is based on (a) cleaning, surface active and sudsing properties of anionic surface active agent or agents, (b) enhancement of antimicrobial properties under acidic conditions, and (c) ready and effective incorporation of miscellaneous ingredients used to impart certain antibacterial, physical properties such as emollient, lubricating, foam boosting, binding, coloring, anti-cracking, perfuming, brightening, transparency, whitening, thixotropic, solubilizing, cleaning, antioxidant, skin nutritive as well as other organoleptic properties.
The soap composition of the present invention consists essentially of:
(a) at least one anionic surfactant present in an amount in the range from about 0.10 weight % to about 95 weight % based on the total weight of the concentrate composition; and
(b) at least one acidifying agent selected from acids of the group which includes acetic acid, adipic acid, ascorbic acid, benzoic acid, citric acid, dehydroacetic acid, erythorbic acid, fumaric acid, glutaric acid, gluconic acid, hyaluronic acid, hydroxyacetic acid, glycolic acid, lactic acid, malic acid, salicylic acid, sorbic acid, succinic acid, tannic acid, tartaric acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, sulfamic acid, carboxylic acid polymers, homo- or hetero-polymerized alpha-hydroxy carboxylic acids including poly lactic acid and poly lactic-glycolic acid and mixtures of two or more said acids, said acidifying agent being present in the concentrate composition in an amount sufficient to provide a pH below 5.0 in aqueous solution.
The bar soap composition of the present invention provides microbicidal protection resulting from its rapid microbicidal action. Typically, rapid microbicidal protection results from significant microbial reduction in an interval of 30 to 60 seconds. In certain instances, it is believed that reductions in an amount up to five logarithmic units may be possible depending upon the type of contact surface and target microorganism.
The composition may also include various other components to impart antibacterial, and other desirable physical and organoleptic properties to the syndet bar soap. These can include antibacterial agents, skin conditioning agents, lubricating agents, coloring agents, moisturizing agents, binding and anti-cracking agents, perfuming agents, brightening agents, UV absorbing agents, whitening agents, transparency imparting agents, thixotropic agents, solubilizing agents, abrasive agents, antioxidants, and skin healing agents. In the preferred embodiment, the syndet soap may contain one or more of these optional agents, with two or more being most preferred. The optional agents can be present in any amount up to 5.0% by weight by category; with an amount between 0.001 and 5.0% by weight being preferred.
The anionic surfactant may be present as a free acid, ester or salt form (e.g., the ammonium, sodium, potassium, calcium and magnesium salts) of a suitable anionic surfactant. Suitable anionic surfactants include at least one of the following:
(a) C6-C18 alkyl- and alkenyl-sulfates;
(b) C6-C18 alkyl- and alkenyl-ether sulfates;
(c) C6-C16 alkyl diphenyl ether disufonates;
(d) C4-C18 fatty acid isethionates;
(e) C6-C18 alkyl- and alkenyl sulfonates;
(f) dialkyl- and dialkenyl sulfosuccinates in which the alkyl or alkenyl groups independently contain from six to eighteen carbon atoms;
(g) alkyl benzene sulfonates in which alkyl group contains from C4-C18 carbon atoms;
(h) alkyl naphthalene sulfonates in which alkyl group contains from one to six carbon atoms;
(i) the mono-n-alkyl and mono-n-alkenyl acyl esters of C2-C4 hydroxylated monocarboxylic acids in which the alkyl or alkenyl group contains from six to eighteen carbon atoms;
(j) the mono-n-alkyl and mono-n-alkenyl alkyl esters of C2-C4 dicarboxylic acids in which the alkyl or alkenyl group contains six to eighteen carbon atoms; and
(k) C4-C16 fatty alcohol sulfoacetates.
By the term xe2x80x9calkylxe2x80x9d as used throughout this specification and the appended claims is meant a monovalent straight or branched chain hydrocarbon radical which can be thought of as derived from a saturated acyclic hydrocarbon by the removal of one hydrogen atom. By the term xe2x80x9calkenylxe2x80x9d is meant a monovalent hydrocarbon radical containing one or more carbon-carbon double bonds, which radical can be thought of as being derived from an unsaturated acyclic hydrocarbon by the removal of one hydrogen atom.
The term, xe2x80x9csalt of a mono-(n-alkyl) or mono-(n-alkenyl)acyl ester of C2-C4 hydroxylated monocarboxylic acidsxe2x80x9d means an ester-salt of a hydroxylated monocarboxylic acid, such as lactic acid, which has been formed by esterification of its hydroxyl function by another acid, and in which its carboxyl function has been converted to a carboxylate salt. An example of such a compound is so-called xe2x80x9cdecyl lactylatexe2x80x9d which is the ester formed by esterifying the hydroxyl group of lactic acid with decanoic acid, and converting the carboxyl function of the lactic acid portion of the resulting ester to the carboxylate salt form.
Similarly, the term, xe2x80x9csalt of a mono-(n-alkyl) or mono(n-alkenyl)acyl ester of C2-C4 hydroxylated dicarboxylic acidsxe2x80x9d means an ester-salt or a hydroxylated dicarboxylic acid, such as hydroxymalonic acid, which has been formed by esterification of its hydroxyl function by another acid, and in which its two carboxyl functions have been converted to carboxylate salts.
By the term xe2x80x9csalt of a mono-(n-alkyl) or mono(n-alkenyl)alkyl ester of C2-C4 dicarboxylic acidsxe2x80x9d is meant an ester-salt of dicarboxylic acid, such as succinic acid, which has been formed by esterification by an alcohol at one carboxyl group.
Preferred anionic surfactants for the compositions include free acids or the ammonium, sodium, potassium, calcium or magnesium salts of 1) alpha olefin (C14-C16) sulfonic acid; 2) C4-C18 fatty acid isethionic acid; 3) C4-C18 fatty alcohol sulfoacetic acid; 4) decyl lactylic acid; 5) lauryl sulfuric acid, and 6) 1,4-dihexyl sulfosuccinic acid.
The anionic surfactant may be present in any amount between about 0.10 weight % to 95.0 weight %. The specific amount employed would be determined by the specific use to which the soap is put and desirable characteristics such as lather formation, cleansing power, etc. to be achieved.
The acidifying agent is present in an amount sufficient to impart a pH at or below 5.0 and may be either organic or inorganic. The acidifying agent may be used individually or in any suitable combination of acids. The acidifying acid may be at least one of the following: includes one or more than one of the following: acetic acid, adipic acid, ascorbic acid, benzoic acid, citric acid, dehydroacetic acid, erythorbic acid, fumaric acid, glutaric acid, gluconic acid, hyaluronic acid, hydroxyacetic acid, lactic acid, malic acid, salicylic acid, sorbic acid, succinic acid, tannic acid, tartaric acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, sulfamic acid, carboxylic acid polymers, homo- or hetero-polymerized alpha-hydroxy carboxylic acids including poly lactic acid and poly lactic-glycolic acid.
Preferably, the acidifying agent is at least one of acetic acid, adipic acid, ascorbic acid, benzoic acid, citric acid, dehydroacetic acid, erythorbic acid, fumaric acid, glutaric acid, gluconic acid, hyaluronic acid, hydroxyacetic acid, lactic acid, malic acid, salicylic acid, sorbic acid, succinic acid, tannic acid, or tartaric acid. Even more preferably, the acid is selected from the group which includes lactic acid, citric acid, ascorbic acid, erythorbic acid, malic acid and adipic acid.
As indicated above, the composition of the present invention may include other optional components added to impart additional antibacterial activity as well as other desirable characteristics including but not limited to biological, physical, organoleptic and other functional properties in the finished syndet bar composition. Each of the optional component classes are typically present in an amount between 0.001% and 5.0% w/w.
Examples of such component classes include antibacterial agents. Compounds suitable for use as antibacterial agents include at least one of benzoic acid, benzoic acid salts, esters of benzoic acid, sorbic acid, sorbic acid salts, esters of sorbic acid, esters of para hydroxy benzoic acid xe2x80x9cparabensxe2x80x9d (methyl, propyl, butyl and ethyl), chlorohexidine, ethyl alcohol, imidazolidinyl urea, isothiazolin compounds, triclosan, 3,4,4-trichlorocarbanilide, dehydroacetate, o-phenyl phenol, quaternium compounds, boric acid, formaldehyde solution, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), fatty acids, fatty acid salts and esters of fatty acids, and antibacterial peptides including nisin and magnanin.
Examples of suitable optional components also include skin conditioning compounds. Suitable skin conditioning compounds include natural products such as plant oils, aloe vera, sea weed extracts, hydrolyzed protein products, lanolin and lanolin esters, vitamins, including vitamin A, C, D and E and their derivatives, fatty acid esters of carboxylic acids, alcohols and carbohydrates.
Lubricating agents which can be employed in the syndet soap of the present invention include natural polymers such as polysaccharide-based compounds, xanthan, arabic, ghatti, carrageenan gums; or other polymers such as starch, cellulose, fatty acid, fatty alcohols, alginic acid, dextrans, modified starch and cellulose polymers, synthetic or semisynthetic polymers including acrylates, carboxylates, sulfated polymers, nonionic agents such as polaxomers, polyols, and silicone based compounds or a mixture thereof.
Coloring agents can also be included. Examples of these include natural carmine, chlorophyls, curcumin and annatto as well as paint-based colors, caramel colors, and FDandC synthetic coloring agents. Binding and anti-cracking agents which can be employed include materials such as natural gums, starch and cellulose as well as other polysaccharides and polysaccharide derivatives, fatty alcohols fatty esters, paraffin, lanolin and lanolin derivatives, hydrogenated oils, glycerides, and ammonium and alkali metal salts.
Suitable perfuming agents can be of natural or synthetic origin. Examples of brightening and UV-absorbing agents include materials such as tinopal while brightening agents can include materials such as titanium dioxide. Materials such as glycerine can be used as transparency imparting agents.
Examples of thixotropic agents which can be employed in the present invention include natural and modified gums and polysaccharides as well as synthetic polymeric compounds as would be know to the skilled artisan.
Solubilizing agents can include water, propylene glycol, ethyl alcohol, fatty alcohols, isopropanol, ethyl acetate, glycolic acid and lactic acid. Foam boosting agents include amine oxides, fatty acid amines, betaines and amphoteric compounds. Examples of emulsifying agents include lecithin, polysorbate 60, polysorbate 65, polysorbate 80, sucrose fatty acid esters, and salts of stearoyl 2-lactylate.
Abrasive agents include materials such as silica, plant seed-coat powders and clays. Skin healing and rejuvenating agents include various plant oils, plant extracts, sea weeds, and sea dwelling organisms. Suitable antioxidants include natural and synthetic antioxidants including ascorbic acid vitamin E and flavanoids.